I had a coupler welded into a MLT keggle so I can attach a thermometer. The coupler extends about 1/2" from the keggle.
I've been looking at Morebeer's 2" and 6" thermometers. I like the idea of the 6" more because it's closer to the center of the mash, but I don't want to wang it with my spoon too many times while doughing in or stirring.
If I only get the 2", it will only extend about 1-1.5" into the mash. I'm sure it will get a reading, but after the mash sits for awhile I don't want to be improperly reading the stratification of temps in the mash.